What are cyanobacteria?

Cyanobacteria, also known as blue-green algae, are microscopic, plant-like organisms that grow naturally in freshwater lakes and ponds. Despite the name, they are not true algae.

Cyanobacteria are often blue-green in colour, but some types may appear green-brown, red-brown, or red. 

Some species can produce harmful toxins called cyanotoxins.

Are cyanotoxins harmful?

Yes. Cyanotoxins can be harmful to people and animals if the contaminated water is:

• Swallowed
• Inhaled as mist or spray
• Touched through skin contact

Symptoms of exposure can include:

• Skin, eye, nose, or throat irritation
• Stomach pain, diarrhea and vomiting
• Headaches, muscle weakness, or fever
• Severe illness or, in rare cases death:
  • Liver or kidney damage
  • Paralysis that makes it hard to or impossible to breathe or affects other muscles in the body.

Children are more at risk because they often spend more time in the water and are more likely to accidentally swallow it.

What does a Cyanobacteria bloom look like?

Cyanobacteria are usually not visible, but in the right conditions, they can multiply quickly and form blooms, which appear as thick mats or scum on the water’s surface.  

Blooms usually appear in late summer, from mid-August to early September. They are often found in warm, shallow, and slow moving water. 

Blooms may look like:

• Green pea soup
• Turquoise paint
• Thick blue-green surface scum
• Solid-looking clumps

Blooms may smell like:

• Grass
• Sewage
• Rotting garbage 

Are cyanobacteria in the NWT?

Yes. Cyanobacteria grow naturally in water across the NWT.

Historically, blooms are rare. However, warmer temperatures and higher nutrient levels, have made blooms more frequent. 

Blooms have been reported in:

• Great Slave Lake, especially near:
  • Yellowknife Bay
  • The North Arm
  • West Mirage Islands
  • Baker Island
• Jackfish Lake, near Yellowknife. Red-brown blooms have occurred every year since 2013.
• Trout Lake near Sambaa K’e
• Other lakes across the Dehcho, South Slave, and North Slave regions.

How can I protect myself and my pets?

If you see a bloom, assume it contains toxins. To stay safe:

• Do NOT drink untreated water from lakes, ponds or wetlands
• Do NOT bathe or swim in discolored, scummy, or smelly water 
• Do NOT boil lake water with a bloom. This will not remove toxins and may make them more concentrated.
• Do NOT let pets:
  • Swim, play, or drink in water with a bloom
  • Eat dried algae along the shore
  • Lick their fur after contact with a bloom

DO :

• Rinse yourself and your pet with clean tap water as soon as possible if you come into contact with a bloom
• Keep children and pets away from affected areas
• Use clean, treated, or bottled water for drinking and cooking

Who do I contact to report a bloom?

If you see a suspected cyanobacteria bloom, please contact your Regional Environment and Climate Change (ECC) Office.